Our overall goal is to gain new information on the abnormal differentiation and function of leukemic cells and to establish better methods for the diagnosis and classification of acute leukemias. Major techniques to be applied are light-(LM) and electron-microscopy (EM) and cytochemistry, scanning EM, and tissue culture. We have established a firm theoretical and technical basis for the proposed research by our previous work on the differentiation and functions of normal leukocytes. Specifically, the objectives are: 1) to ascertain if defects in acute leukemia cell maturation correlate with "blocks in differentiation" at stages of secretory pathway by analyzing the localization of peroxidase and other granule enzymes; 2) using LM, EM and histochemistry, to subclassify acute leukemias into distinct cell lines, with emphasis on developing and testing new methodologies.